1. Field of the Invention
The present invention relates to a photoelectric switch of the separate type, which is formed with a head and a main body, for detecting an object in a predetermined detection area.
2. Description of the Related Art
Photoelectric switches have been used for detecting objects in production lines of factory. The photoelectric switch projects light to within a predetermined detection area, receives light returned from an object, and determines whether or not an object to be detected is present within the detection area by receiving light returned from the object.
In the photoelectric switch of the transmission type, when an object to be detected does not exist within a detection area, light projected from a light projecting section enters a light receiving section. In this case, when a level of the amount of received light in the light receiving section is lower than a predetermined threshold value, it is determined that an object to be detected is present there. In the photoelectric switch of the reflection type, when an object to be detected is present, light projected from the light projecting section is reflected by the object and enters the light receiving section. In this case, when a level of the amount of received light in the light receiving section exceeds a predetermined threshold value, it is determined that the object is present there. A sensitivity of the photoelectric switch is adjusted by varying the threshold value.
One of those photoelectric switches is of the separate type in which the photoelectric switch is separated into a head and a main body. The head contains mainly a light projecting section for projecting light and a light receiving section for receiving light returned from an object to be detected. The main body contains mainly a control unit for controlling the light projecting section and the light receiving section, and a power supply circuit. Further, it contains a display unit for displaying the amount of the received light in the head and a threshold value, and a switch for adjusting the threshold value. The display unit of the main body displays a tolerance level of the light-receiving amount with respect to the threshold value.
The photoelectric switch of the separate type may be used such that when a broad space does not exist near the object to be detected, only the head is located near the object while the main body is located farther from the object.
In installing the photoelectric switch of the separate, reflection type, to prevent noise from giving rise to error, a position of the head must be adjusted, for example, in such a manner that when an object to be detected exists within the detection area, the light-receiving amount is sufficiently high with respect to the threshold value, and when the object does not exist within the detection area, the light-receiving amount is sufficiently low with respect to the threshold value.
In this type of the photoelectric switch, however, when the main body is located far from the head, it is impossible that the operator adjusts the head position while checking a display by the display portion in the main body. This makes it difficult to accurately adjust the head position and impairs workability in adjusting the head position.
Accordingly, an object of the present invention is to provide a photoelectric switch of the separate type which can accurately and easily check information on a process carried out in the main body even when the main body is located far from the head.
Another object of the present invention is to provide a photoelectric switch of the separate type which can accurately and easily adjust a position of the head even when the main body is located far from the head.
These objects can be achieved by a photoelectric switch of the separate type, according to a first aspect of the present invention, which projects light to a detection area and detects the presence or absence of an object to be detected within the detection area by receiving light returned from the detection area. The photoelectric switch comprises: a head that includes at least a light receiver for outputting a light reception signal based on a light receiving state of light returned from the detection area; and a main body, connected to the head by a signal line, for receiving a light reception signal output from the light receiver through the signal line. In the photoelectric switch the main body includes a processor for detecting the presence or absence of an object to be detected within the detection area by use of the light reception signal received through the signal line from the head, and the head includes an indicator for displaying information on the process carried out by the processor by the main body. The information on the process carried out by the processor is information regarding the detection of the presence of the object executed by the processor.
In the photoelectric switch of the invention, the light receiving section of the head outputs a light reception signal based on a light receiving state of light returned from the detection area, and the light reception signal is applied through the signal line to the main body. In the main body, the processor detects the presence or absence of an object to be detected within the detection area by use of the light reception signal received through the signal line from the head. In the head, the indicator displays information on the process carried out by the processor in the main body.
Thus, the indicator of the head displays information on the process in the main body. Therefore, when the main body is located farther from the head, the operator/user checks information on the process by the processor while watching a display by the indicator of the head.
In the photoelectric switch of the invention, it is preferable that the processor includes: a generator for producing a process signal based on a light reception signal, which is received from the head through the signal line in order to detect the presence or absence of an object to be detected within the detection area; a setting unit for setting a reference value used for determining if the object to be detected is present within the detection area; a detecting unit for determining if the object to be detected is present within the detection area by comparing a process signal produced by the generator with a reference value set by the setting unit; and a calculator for calculating a relative value of the process signal produced by the generator to the reference value set by the setting unit in the form of a tolerance level, wherein an indicator displays a tolerance level calculated by the calculator as information on the process by the processor.
In this case, in the main body, the generator produces a process signal based on a light reception signal, which is received from the head through the signal line in order to detect the presence or absence of an object to be detected within the detection area. The setting unit sets a reference value used for determining whether or not the object to be detected is present within the detection area. The detecting unit determines if the object to be detected is present within the detection area by comparing the process signal produced by the generator with the reference value set by the setting unit. The calculator calculates the relative value of the process signal produced by the generator to the reference value set by the setting unit in the form of a tolerance level. In the head, the indicator displays a tolerance level thus calculated by the calculator as information on the process by the processor.
Thus, the tolerance level is displayed by the indicator of the head. Therefore, even when the main body is installed at a position located far from the head, the operator/user may adjust a position of the head while watching a display by the indicator of the head. Accordingly, the operator/user can accurately and easily adjust a position of the head so that a tolerance level is sufficiently large. Further, workability in adjusting the head position is improved. The operator/user checks if the photoelectric switch stably performs an object detecting operation by watching a display on the head.
Further, in the photoelectric switch of the invention, it is also preferable that the main body further includes a display unit for displaying at least one of a process signal produced by the generator, a reference value set by the setting unit, and a tolerance level calculated by the calculator.
In this case, in the main body, at least one of the process signal, the reference value and the tolerance level is displayed by the display unit. Therefore, the operator/user may recognize the process signal, the reference value or the tolerance level in an easy manner by the display unit of the main body.
Furthermore, in the photoelectric switch of the invention, it is further preferable that the main body further includes a power supply circuit which is connected to the head by a power line, and supplies a voltage based on the tolerance level calculated by the calculator as a power voltage, for driving the head, to the head by way of the power line, and the indicator displays the tolerance level calculated by the calculator of the main body on the basis of the voltage supplied through the power line from the main body.
In this case, the voltage based on the tolerance level calculated by the calculator of the main body is applied as the voltage for driving the head to the head by way of the power line. The tolerance level is displayed by the indicator, on the basis of the supplied voltage. Therefore, a single line is common to the power line for supplying the power voltage for driving the head and the signal line for transmitting the tolerance level. As a result, the increase of the number of signal lines, caused by the display of the tolerance level in the head, is restricted.
Further, in the photoelectric switches of the invention, it is more preferable that the head further includes a light projector for projecting light to the detection area.
In this case, the light projector of the head projects light to the detection area, and the light receiving section of the head receives light returned from said detection area.
The above-mentioned object can be achieved by a photoelectric switch of the separate type, according to a second aspect of the present invention, for detecting an object to be detected in a detection area in a manner such that the photoelectric switch projects light to the detection area and receives light returned from the detection area. The photoelectric switch comprises: a head that includes a light projector for projecting light to within the detection area and a light receiver for outputting a light reception signal based on a light receiving state of light returned from the detection area; and a main body, connected to the head by a signal line and a power line, for receiving a light reception signal output from the light receiver through the signal line. In the photoelectric switch the main body includes a processor for detecting the presence or absence of an object to be detected within the detection area by use of a light reception signal received through the signal line from the head, and a power supply circuit for supplying a voltage representative of information on an operation of the head as a power voltage for driving the head to the head by way of the power line, and the head includes an operating portion for performing a predetermined operation in accordance with the information represented by the voltage supplied from the main body through the power line.
In the photoelectric switch of the invention, a light receiver of the head outputs a light reception signal based on a light receiving state of light returned from the detection area. In the main body, a processor detects the presence or absence of an object to be detected within the detection area by use of a light reception signal received through the signal line from the head. Further, a voltage representative of information on an operation of the head is supplied, as a power voltage for driving the head, to the head by way of the power line. In the head, a predetermined operation is performed in accordance with the information represented by the voltage supplied from the main body through the power line by an operating portion.
Thus, a single line is common to the power line for supplying the power voltage for driving the head and the signal line for transmitting the information of the operation of the head. As a result, the increase of the number of signal lines, caused by the information on the head operation to the head, is restricted.
In the photoelectric switch of the invention, it is preferably advantageous that the information on the operation of the head includes information on the process by the processor, and the operating portion includes an indicator for displaying the information on the process by the processor of the main body on the basis of the voltage supplied from the main body through the power line. The information on the process by the processor is information regarding the detection of the presence of the object executed by the processor.
In this case, the voltage representative of the information on the process by the processor is applied as the power voltage for driving the head and is supplied through the power line to the head. In the head, the information on the process by said processor of the main body is displayed by the indicator on the basis of the voltage supplied from the main body through the power line.
Thus, a single line is common to the power line for supplying the power voltage for driving the head and the signal line for transmitting the tolerance level. As a result, the increase of the number of signal lines, caused by the display of the information on the process by the processor, is restricted.
In the above-mentioned photoelectric switch of the invention, it is further advantageous that the indicator displays information on the processing by the processor in terms of a numerical value.
In this case, information on the processing by the processor of the main body is displayed in terms of a numerical value by the indicator of the head. Therefore, the information on the processing by the processor of the main body may easily be checked on the display in the head.